Simplify:  $$\left(\sqrt[3]{\sqrt[3]{343}}\right)^3 \times \left(\sqrt[3]{\sqrt[3]{216}}\right)^3$$​​

Correct option is B

Given: 

​$$\left(\sqrt[3]{\sqrt[3]{343}}\right)^3 \times \left(\sqrt[3]{\sqrt[3]{216}}\right)^3$$ 

Concept Used: 

​$$( x^a)^n = x^{a\times n}$$ 

Solution:  

​$$=\left(\sqrt[3]{\sqrt[3]{343}}\right)^3 \times \left(\sqrt[3]{\sqrt[3]{216}}\right)^3 \\ \ \\ = \left(\sqrt[3]{7}\right)^3 \times \left(\sqrt[3]{6}\right)^3 \\ \ \\ = \left({7}\right)^{\frac{1}{\cancel3}\times \cancel 3} \times \left({6}\right)^{\frac{1}{\cancel3}\times\cancel3} \\ \ \\ = 7 \times 6 \\ \ \\ = 42$$​​